i notice that, when using my garmin to track our progress (in a bus) in Yucatan that my GPS showed us off the highway a few miles when in fact we were on it…maybe they dont have good sat reception there? Otherwise the unit worked pretty well, though I also noticed that I couldnt get the city detail like I can here in the conus. My model is the Garmin 250w and it (supposedly) comes with US, Canada, and Mexico.
alternatively the map may have had the highway in the wrong location (perhaps it was repaved on an alternate alignment and the map company never figured it out).
Skelly76, sometimes due to bad satellite geometry in the sky if your GPS is not WAAS enabled, you might be off as far as 20~30 meters, but to be off by a few miles, I would suspect that it might be map problem.
I lost gps signal today going into Puebla. Both FMS’s went into dead reckoning mode. First time this has happened to me and I have spent a lot of time in places more remote than Mexico. They worked fine going out.
I don’t think it has to do with the remoteness of a place. I’ve been in many remote places where I got great GPS signals. It all has to do with the satellites.
Garmin has an article at www8.garmin.com/aboutGPS/ about why you received a degraded signal.
Shame on you for not checking RAIM
GPS, RAIM.
Man am I glad we don’t have any of that high tech stuff. 
+1
Maps for Mexico are nothing more than basemap detail and are not very accurate. According to some of my GPS tracks in South and Central America, I have walked on water many times! 
I was standing on Lincoln St in South Beach. Not on a boat, which would’ve been much better…
If you had a marine map it would have figured it out!
On the other hand my maxipad had us right on the taxiway the other night. Kind of cheating since it was using assisted GPS by then.
You use maxi pads??? T.M.I. 
It was beautiful VFR, I was enjoying the view of the Volcanoes, and had it backed up with VHF raw data on the RMI’s. Had there been any weather I would have used the ILS anyways & you’ve shown off your handheld to us before I know you don’t have RAIM monitoring or approach capabilities with that.
HAHA- we only use that for the XM weather, we have approach capable GPS’s on the pedestal.
The Problem with the Trimble isn’t RAIM it’s a matter of RAM…